1. Field of Invention
Embodiments of the present invention relate generally to semiconductor memory devices, and more particularly, to a semiconductor memory device such as a nonvolatile memory device.
2. Description of the Related Art
Semiconductor memory devices, which store data, are generally classified as volatile memory devices or nonvolatile memory devices. Volatile memory devices lose stored data in the event of power interruption, whereas nonvolatile memory devices retain stored data even if power is interrupted.
A flash memory device is a type of nonvolatile memory device that is capable of electrically writing and erasing data, and is suitable for high density and high capacitance. A unit cell of the flash memory device may include a stack gate structure in which a floating gate and a control gate are sequentially stacked on an active region. A capacitive coupling may exist between the floating gates of unit cells adjacent to each other along the direction in which the control gate extends. This capacitive coupling may cause a read error in an operation mode for selectively reading data stored in a unit cell.